An overheated engine can be the beginning of the end of your car's life. Knowing your way around a hot engine and how to prevent one from happening again can keep your car on the road longer, to make sure you know what to do the next time your temperature gauge is reading "H."
Like the label around the radiator cap cautions, approach an overheated engine with extreme care. Overheating in a car is the function of two laws of physics--heat and pressure--and when the two get out of control, danger prevails. Coolant allows radiator fluid to be heated up to 264 degrees F without boiling over. Combine that with a radiator cap rated at 18 PSI, and you have the makings of a scalding geyser. It's best to allow the engine to cool down. Then you can add coolant to the reservoir. If you can safely feel the top radiator hose, test it for hardness. If it's hard, that's not good--too much pressure. If it's soft, you might be able to slowly ease off the radiator cap. Use gloves or a rag, anything to put some distance between you and the heat of the coolant. Then you can add to the radiator directly. If you're hesitating about any of this, seek professional help.
Is the engine really overheated? Steam and smoke do not a mean an engine is overheated. While a steaming engine can be just as dangerous as an overheating one, your observations can be a key to getting the car repaired efficiently and economically.
So where is the smoke coming from? The smallest pinhole in a hose can spray coolant onto a hot part of the engine like an exhaust manifold and create steam. Your job is follow the mess back to the source. Just as important is to note what the gauges say. If your temperature gauge is in the red zone, your car is overheated and you must stop the car. To continue is to risk engine damage. So you either have an overheated car with a gauge saying so or a steaming vehicle that is certain to overheat if you continue to drive.
With the exception of sudden motor oil loss, there is nothing in a car as significant as an overheated engine. To ignore a hot light or a red lined temperature gauge is to flirt with engine seizure. Coolant rather than plain water is used to accommodate the high temperatures that the engine generates in the course of powering the car. Any breakdown in the the closed loop of a cooling system, whether it be leakage or the failure of a main component (radiator, water pump, thermostat), will cause a overheated engine. The previously mentioned oil loss will also cause an overheated engine due to lack of lubrication. This would be the result of gross neglect. Assuming instrumentation is working correctly, engine loss due to an overheated engine does not need to happen. Not every overheated engine ends up in the shredder, but it is a traumatic event for a car.
The overheated engine doesn't just happen. Even in the case of a thermostat that is stuck closed, there are warning signs prior to the temperature gauge going up. In this case, there would be a lack of heat inside the car because there is no coolant flowing to the heater core. The same symptom will prevail when there is not enough coolant because of leakage. If there is a spot on your driveway, you may be losing coolant. There are some conditions that are little tougher to diagnose, such as an intake manifold gasket leak in which the coolant is burning off before it hits the pavement or an engine head gasket leaking coolant into the crankcase. In both cases, the vehicle will need coolant, so if you're adding coolant, you need to get to the root problem or risk an overheated engine.
Maintenance, inspection and reaction can prevent an overheated engine. Maintenance--either by a professional or yourself--will prevent an overheated engine. As service procedures like oil changes take place, the repeated need for coolant will alert you to a problem. This will occur as you or the technician top off the fluids. Inspection for leaks in the area around your vehicle as you enter or exit can also indicate a need for attention. Finally, you need to react to the signs and either seek professional help or tackle the problem yourself so that a pegged temperature gauge isn't the first indication of an overheated engine.
